1. Field of the Invention
The present invention relates generally to flexible hoses, and in particular to a flexible hose section which controls dynamic stresses in a system with components which are subjected to differential dynamic forces.
2. Description of the Related Art
Conduit and piping systems for conveying fluids and bulk materials are used in a wide variety of applications. Various components for such systems have been devised to accommodate different fluids and materials and to operate in particular environments. For example, some of the components of such systems are fabricated from flexible metal hose, which offers the advantages of durability, flexibility, relatively low cost and adaptability to various sizes, configurations and materials.
Flexible metal hose has been used for many years to interconnect components which move relative to each other. Some of the common configurations of flexible metal hose include spiral-wound, edge-interlocked hose wherein the edges of a strip of sheet metal are interlocked on a hose winding machine to permit limited deflection of the resulting flexible metal hose. Corrugated flexible metal hose, on the other hand, can be roll-formed or spiral-wound using special rollers which shape the corrugations in either annular or spiral (helical) arrangements. The corrugations provide flexibility and permit a corrugated pipe or hose section to be bent and shaped more easily than a comparable hose section with smooth walls. Moreover, corrugations can permit a hose section to be bent around a relatively tight radius, and can dissipate dynamic stresses associated with the vibration of the components to which the flexible hose section is attached.
Corrugated flexible hose sections can have corrugations of different diameters, such as a bellows-type arrangement with the largest-diameter corrugations in the center and corrugations of decreasing diameters toward the ends whereby maximum flexibility is achieved in the center with increasing stiffness toward the ends. Such bellows-type configurations tend to be relatively efficient at dissipating vibrational energy along their entire lengths since their varying stiffness ratios tend to transmit vibrational energy toward their centers for dissipation.
Hybrid flexible metal hose sections have also been fabricated from corrugated sheet metal bands which are spiral wound with their edges interlocked. The resulting hose sections can provide the advantages of both interlocked-edge and corrugated types of flexible metal hose. Such hybrid hose designs can combine the advantages of both of these flexible metal hose types. At least for example, see the Thomas U.S. Pat. No. 5,494,319.
Exhaust systems for internal combustion engines are examples of relatively severe environments in which the operating characteristics of flexible metal hoses can be used to advantage. Flexible metal hose sections are often used for connecting the exhaust pipes from vehicle internal combustion engines with manifold mufflers, tail pipes and other exhaust system components. Flexible metal hose sections are commonly used in the exhaust systems of tractors of tractor-trailer truck rigs because of their flexibility, temperature resistance and corrosion resistance when fabricated from suitable materials, such as stainless steel.
Exhaust systems in general and vehicle exhaust systems in particular must perform reliably under relatively severe operating conditions, which can include temperature extremes, corrosive environmental factors and dynamic stress loading. Dynamic stresses in an exhaust system can originate from vibrations associated with the engine and movement of the vehicle. Such dynamic stresses include axial, lateral and diagonal forces, all of which can normally be effectively attenuated and controlled by flexible metal hose with corrugations and/or edge interlocking. However, torsional forces caused by the differential rotation of the exhaust system components connected by a flexible metal hose section can inflict significant damage, particularly when the flexible hose section ends are fixedly secured and the flexible section design is rigid with respect to rotational forces. Such dynamic torsional forces can lead to premature metal fatigue, cracking and failure of exhaust system components, including previous designs of flexible metal hose.
The present invention addresses these considerations in connection with the application of flexible metal hose to applications involving dynamic stresses. Heretofore there has not been available a dynamic stress controlling flexible hose section with the advantages and features of the present invention.